What is the crank sensor in Volvo 740 turbo 1989?

Answer 1

I am not familiar with your particular make and model of vehicle, but that's not critical as most vehicles today use a crank sensor, or a similar device. Because of my lack of familiarity, this answer will be generic in nature, until an expert on your vehicle can improve this answer. In order for the engine management computer to function, it HAS to know the revolutions per minute at which the engine is running, and it has to know which piston [particualrly #1] is in what position [i.e., intake, compression, power, or exhaust stroke]. Most crankshaft position sensors are combination optical and electrical/electronic devices, meaning that the device senses the passing of a visible mark on the crankshaft pulley, and electrically sends that info to the computer. There is another type of sensor that instead of optically sensing, records the passing of small magnet. These devices usually use a magnetically sensitive transistor [I think it's called a "Hall effect" transistor. Regardless of the details, a "crank sensor" senses the rate of rotation of the crankshaft [thus the RPM], AND senses the position of the pistons. It electrically sends that info to the engine management computer so it can determine many factors of engine running status, and make necessary adjustments [amount of fuel, fuel mixture, ignition timing, and many more]. Until an expert can correct/improve this answer, I hope I will give you a basic understanding.